1. Field of the Invention
The present invention relates to a blow molding machine including an extrusion or co-extrusion head for forming a preform hose which is associated with an extruder, a hose handling device, a device for removing finished articles, at least one horizontally separated blow mold formed of upper and lower half-molds, a device for vertically displacing at least one of the upper and lower half-molds between an open mold position in which the upper half-mold is spaced from the lower half-mold, and a closed mold position in which the upper and lower half-molds engage each other, and a device for locking the upper and lower half-molds in the mold closed position.
2. Description of the Prior Art
The manufacture of low-waste, seamless, three-dimensional blown article is a well known technology since long ago. The machines, which are used to this end, include, as a rule, a handling device formed as a gripper, if necessary, a field programmable six-axes robot for placing preforms into a cavity formed in a blow mold. The production of seamless blown articles or parts results from the fact that upon closing of the mold, portions of the circumference of the preform, i.e., the extruded hose are not squeezed out, but rather the entire circumference of the preform is surrounded by the mold cavity. Nevertheless, both ends need be closed by squeezing to enable the blowing up of the preform by injecting gas through a needle or a mandrel.
German Publication DE-Z, Plastvezarbeiter (Plastic Processor), 44, 1993, No. 12, p.p. 44-49 (DE-Z) discloses the use of conventional blow molding machines such, e.g., as disclosed in German Patent Publication DE 195 19 094 A1, in a completely automatic process by providing a mechanical gripper which lifts a hose-like preform, which is formed with a shape corresponding to the shape of the mold cavity, from a hose-producing nozzle and places it into the mold cavity. As a rule, the free-programmable, six-axes robot places the preform into the mold completely automatically, with the mold being then closed with a vertical closing device.
DE-Z further discloses that slides can be provided in a mold for manipulating a preform placed into the mold. The above-described slides are used primarily for blown articles with small curvatures. The slides are displaced in the separation plane of the mold and prevent squeezing-out of the preform upon closing of the mold. After closing of the mold, the slides are withdrawn, and the preform is blown up.
However, with the use of the conventional blow molding machines, placing of a preform in a cavity with very small radii is very difficult or at all impossible because the preform, in this case, has a tendency to jump out at the curve. Further, because of an early contact of the hose with the surface of the cavity of the lower half-mold, cooling of the preform occurs which adversely affects the subsequent process. Finally, the closing system which is used with the known blow molding machines and which is based on using of spars, is very expensive. Furthermore, the conventional closing devices are not well suited for use with multi-station blow molding machines.
Accordingly, an object of the present invention is to provide a blow molding machine for producing low-waste, three-dimensional articles of the above-described type having improved and more varied operational characteristics and which at the same time would insure a more economical production of the articles.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a blow molding machine that includes means which in the open position of the mold, i.e., when the upper half-mold is spaced from the lower mold, pivots the upper half-mold about a horizontal axis by approximately 90xc2x0 and/or displaces the upper half-mold in a horizontal plane substantially linearly. The inventive blow molding machine for producing of low-waste, three dimensional articles permitted to use per se known locking systems, the use of which in the conventional blow molding machine was not considered previously, to insure the application of necessary locking and retaining forces. Further, the use of the know locking system permitted to eliminate the need in expensive closing devices for closing the molds and which were used with conventional blow molding machines. Thus, the present invention provides for linear displacement of the upper half-mold in a vertical plane between the mold closed and open positions, and for pivoting of the upper half-mold about a horizontal axis and/or for linear displacement of the upper half-mold in a horizontal plane in the open position of the mold.
The upper half-mold, by being pivoted, according to the present invention, in its lifted position about a horizontal axis by approximately 90xc2x0, becomes easily accessible to a robot without additional large expenses. This significantly simplifies placing of the preforms. Besides, a significant time saving is insured because the upper half-mold is in the same position as the preform-placing robot which, after the upper half-mold having been pivoted, has sufficient free space for manipulations. After the placement of the preform, the upper half-mold need only be pivoted back and lowered onto the lower half-mold. In contrast, with the conventional concept, time-consuming manipulations of the lower half-mold are needed for placing a preform hose which is extruded at a stationary point.
In case the upper half-mold is additionally displaced in a horizontal plane, in a simple manner, the operation of a multi-station system can be effected based on a principle of a so-called wheel machine, with more than two molds being associated with the same extrusion unit, which is particularly advantageous for a sequential extrusion or co-extrusion. An upper half-mold which, in this case, is displaced along two linear axes, enables an operation at which the lifted upper half-mold, after removal of a finished article and after or before it is moved to the following station, is pivoted by 90xc2x0 in a vertical plane, enabling placement of so-called placing parts, e.g., clips, ets. by a robot, a feeding system, or operator.
According to a further development of the present invention, there is provided a carriage in which the upper half-mold is received and which is displaced horizontally. The carriage is equipped with a lifting device for lifting and lowering the upper half-mold from and toward the lower half-mold at the blow station. At that, the mold separation lines can deviate from a substantially horizontal jointing plane because the upper half-mold during the locking process can be displaced by another device.
According to the present invention, a pivoting device is provided for pivoting the upper half-mold in the vertical plane. Such a device can be formed, e.g., as a conventional motor-driven rotary drive.
According to the present invention, the locking device includes locking cylinders and mating lock bars provided on respective backing plates of the lower and upper half-molds. This locking device is particulary advantageous when more than one upper half-molds are associated with a single lower half-mold mold because it is only the lower half-mold which is provided with high-quality and, therefore, expensive locking cylinders.
When oppositely arranged slides are provided in each region of the cavity of the lower half-mold with a narrow radius and which, upon placement of a preform hose close, if necessary, gradually, the preform hose does not jump out of the cavity even when the cavity has one or more narrow radii. The upper half-mold, which in this case represents a so-called pot cover for the lower half-mold, is provided with a recess for formlockingly receiving at least one pair of slides. The drive elements for driving the slides and associated control elements do not form part of the blow mold. Rather, they are provided in the portion of the machine frame in which the lower half-mold is received. Because it is not the slides and their drives apply the closing force but a special locking system, the slides and their drives are inexpensive.
According to the present invention, a tempered air is injected into the cavity of the lower half-mold. Thereby, no impermissible cooling of the preform hose takes place, and no walls with increased thickness are formed during the blow-up process.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.